RNA plays an important role in cellular regulation--either by its presence in active form or by its total absence. A number of proteins have been shown to be involved in regulating RNA synthesis and RNA processing in Escherichia coli--among these are RNA polymerase, rho and RNase III. We have described an enzyme from chick embryos (RNase DII) which is an analogue of RNase III. These proteins are involved in the synthesis or inhibition of synthesis of specific species of RNA and in the processing of RNA. Comparison of ribosomal RNA gene sequences between rat and chicken suggest that a common sequence in the transcript may represent a specific cleavage site for rRNA processing enzymes. Another enzyme which may be involved in regulation of RNA synthesis is RNaseH. The function (or for that matter, the necessity) of RNaseH remains unknown. We have generated a bacterial mutant, using recombinant DNA technology, which is defective in RNaseH. These cells grow only in the presence of a complementary RNaseH gene thereby demonstrating the requirement for RNaseH in cell growth. The objective of this research project is to determine the method by which several of these enzymes act to regulate RNA synthesis in E. coli and chick embryos.